problem posts

Rsync and dealing with “some files vanished” warning

I use rsync for backups, site deployments, and other purposes where I need to sync two folders. It took a little while to figure out, but has been great for those purposes since. Every once in a while, though, I run into issues with it. Recently, I set up an rsync script to back up most of the files on my entire computer. Since this takes a while and the computer is actively running during the backup, things can change while it is still running. This can lead to some errors like “rsync warning: some files vanished before they could be transferred”. Even though this is a warning, and the sync works perfectly fine, it returns a non-zero exit code. This caused my script to stop and thus the rest of the backup activity didn’t finish.

I looked for an option or simple solution to allow it to go on without complaining.

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MySQL: DELETE with sub-query on same table

I had an issue with a MySQL query containing a sub-query recently where it worked fine when done as a SELECT query, but gave an error when switching it to a DELETE query. The error given was something like ‘You can’t specify target table “items” for update in FROM clause’. The sub-query was referencing the same table as the main query, which apparently can’t be done directly in MySQL because the table will be modified during deletion. But there is a sort of a hack I found in this StackOverflow answer, among others, to force it to create a temp table and allow it to work.

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Swap file for composer out of memory problems

PHP’s defacto package manager, composer, has long required large amounts of memory to do updates for larger projects, often more than servers or virtual machines have. The script will die with an out of memory error, or more recently, the simple message “Killed”, and do no work in these situations. The normal procedure is to develop locally, deploy local lock file (composer.lock) to the server, and run composer install instead of update. But I’ve recently moved to doing most of my development in VMs, so I have had to work around this problem to get things installed or updated. A swap file is the solution for Linux machines provided in the official docs and expanded in a StackOverflow answer.

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Firefox: Weird rendering with high contrast mode

I figured out why Firefox 91+ seemed to break some CSS rendering for me (as I blogged about a few weeks back): high contrast mode. I’ve used the accessibility setting “Increase Contrast” on Mac OS for some time to make it easier to see some interface elements. Apparently, via Firefox 91 release notes, “Firefox now automatically enables High Contrast Mode when ‘Increase Contrast’ is checked on MacOS”.

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